Distillation of acid-treated oils



Aug. 7, 1951 Caustic and Promoter M. c. K. JoNEs ET AL DISTILLATION OF ACID-TREATED OILS Filed Sept. 24, 1948 Vacuum A zrze Vap 07 Z #73 5' tom/9e 7072K Condenser Reflux 1 file MCIK. WC".

$901119 l Tank the acid treated charge.

Patented Aug. 7, 1951 DIS'IILLATION OF ACID-TREATED OILS Minor 0. K. Jones, Mountainside, and Edward 0. Eulhardt, Union, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application September 24, 1948, Serial No. 51,038

Claims.

This invention relates to processes in which oils which have been acid treated are heated, for example to distill the oils. The subject matter of this application relates to that disclosed in United States application 700,984, now Patent No. 2,455,679; the subject matter of the present application constituting a continuation-in-part of the subject matter of the said U. S. application. Patent No. 2,455,679 discloses, and claims the use of a critical amount of naphthenic acid soaps, or sodium naphthenate together with sodium hydroxide in the distillation of an acid treated oil. The present invention discloses and claims the use of a critical amount of alkali phenates and sodium hydroxide in processes such as the distillation of acid treated oils.

The invention may be used in conjunction with the distillation of various types of mineral oils such as naphthas, petroleum lubricating oils, shale oils, hydrogenated tar or coal oils, etc., which have been acid treated, have been neutralized, and which on distillation develop certain undesirable characteristics due to decomposition of compounds containing the acid radical. Since the greatest advantages of the present process are obtained when it is applied to the redistillation of acid treated naphthas, and especially of acid treated cracked naphthas, the same will be described in more detail in conjunction with its last mentioned application.

Redistillation of a cracked naphtha which has been treated with sulfuric acid is the usual method employed for improving the color and lowering the gum and sulfur content of the stock, these changes being effected through removal of polymers. In the course of this distillation, sulfur dioxide is often evolved through the thermal breakdown of sulfuric acid esters present in This gas passes out of the still in company with the overhead products, resulting in serious corrosion of both overhead equipment and furnace tubes and heaters. Furthermore, deposits in the tubes of the reboiler section from this decomposition of sulfuric acid esters reduce heat transfer coefficients causing rapid rise in the tube metal temperatures and forcing shutdowns for cleaning after runs of short duration.

It has been suggested that sodium hydroxide be employed to neutralize esters present in the oil prior to distillation. These proposals are based on the principle that basic substances such as sodium hydroxide will neutralize the acid esters, or will react with sulfur dioxide evolved through the breakdown of the esters so as to reduce the corrosion problem which is encountered. While use of sodium hydroxide is more or less effective for eliminating the effect of S02 released through ester breakdown it has been found that use of sodium hydroxide greatly increases the deposits formed in the tubes of the reboiler section of the.

distillation equipment utilized. Consequently, sodium hydroxide of and by itself is not effective in eliminating the problems both of the sulfuric acid ester breakdown and of deposit formation.

It has also been proposed to utilize basic materials other than sodium hydroxide to perform the same functions. For example, it has been proposed to use oil soluble soaps in place of the sodium hydroxide to avoid the troublesome deposits in the distillation equipment. While the use of oil soluble soaps is effective for the desired purposes, use of these soaps is not economically attractive since they are generally quite expensive, and certainly more expensive than sodium hydroxide.

It is, therefore, the principal object of this invention to provide a process for distilling petroleum oils which have been acid treated, utilizing sodium hydroxide in large part together with small quantities of certain promoters which effectively eliminate the deposit forming tendencies of sodium hydroxide used alone. In accordance with these objectives the present invention contemplates the use of somewhat less than of the quantity of sodium hydroxide required to fully neutralize the acid esters together with sufiicient basic promoters to complete the neutralization.

The nature of this invention will be more fully understood in the light of the following comments directed to the mechanism of ester breakdown and deposit formation during distillation. It is clear that in the case of a petroleum oil which has been treated with sulfuric acid and is subsequently distilled without neutralization of acid. esters, that these esters will break down evolving sulfur dioxide. Also during this distillation a certain amount of deposit formation Will occur in the distillation equipment due to the thermal break- 3 down and subsequent coking of the organic material present. Considering now the case in which the acid treated oil is first completely neutralized with sodium hydroxide, it has been found that sulfur dioxide evolution may be substantially avoided. Thus if a considerable excess of sodium hydroxide is employed, it is possible to substantially eliminate the formation of the sulfur dioxide. However, the presence of sodium hydroxide during distillation seriously contributes to the formation of deposits in the distillation equipment. Furthermore, the deposits formed, due to the presence of sodium hydroxide are extremely hard deposits which are exceedingly hard to remove from the distillation equipment. Presence of these deposits causes local overheating of the distillation equipment, and necessitates complete plant shut downs for cleaning the equipment. Analyses of these deposits indicate that the deposit comprises sodium sulfatewhich acts as a cementing material to form exceedingly hard coatings together with the coke formed during distillation. Experiments have clearly indicated that hard, difiicult to remove deposits are built. up.

When sodium hydroxideis used alone as the neueas agent jIn ,order to overcome this difiiculty; that is, the dep osition of a hard deposit when using sodium hydroxide, it has now been discovered thatlcertain promoters may be used with a critical concentration of sodium hydroxide in order" to fully achieve the object of elmininating the hard deposit characteristic of employing sodium'hydroxide. In accordance with this invention it-has been discovered that something less than-100% of the amount of sodium hydroxide should be employed which would fully neutralize esters present. "Sufficient oil soluble phenols should be used. Petroleum phenols are phenolic compounds formed during cracking op erations and comprise principally C1-C2o mono-- substituted alkyl phenols. It has also been found advantageous to use a small amount of a heavy oil, such as a clear fuel oil alon with the caustic and promoter to act as a vehicle to carry along any sediment formed in the heater section of the step.

Referring now to the figure, the apparatus will be briefly described in conjunction with the method of operating the same.

Thefac'id treated oil. from tank I ;and the caustic containing the promoter from tank 2 are passed by means of pumps 3 and 4 through meters 5 and 6 and line '1 into the re-run battery. About 0.5% ofa heavy oil may also be added if desired. The re-run battery, in case of re distilling naphtha,-may consist of tower 8 which is heated by means of a closed steam coil 9 at the bottom thereof. The tower is provided with the usual bell cap plates. All the unvaporized residue is removed th'rough line H into residue tank l2. Overhead distillate which leaves the tower through line I3 is condensed in condenser TABLE I N aOH Added as Free Caustic to Distillation Stock FDeposit lbestRSlowing orme on 2, e notion Test Contact Promoter Added Hemery Foul Oven stock Per Cent ing Tube "With N o Lbs/Dbl. of Theo- Treatment retical* VoLper, cent Grams Per. cent 1 l- 0.16 133 None 0.5959 63 2 0. 12 100 2 .0% crude sodiun naphthenatenn 0. 8843 85 3 0. 114 95 2.0% crude sodium naphthenateh -0. 2368 .86

promoters should beemployed with this sodium hydroxide to complete the neutralization. By this means it is possible to substantially eliminate the ,hard deposits normally characteristic of the employment of sodium hydroxide in this process, and at the same time to substantially eliminate the evolution of sulfur dioxide.

Suitable promoters which may be employed in the practice of this invention include naphthenic acidsoaps; such as sodium naphthenate, amines, tetra alkyl ammonium hydroxide, and oil soluble soaps. The present invention is particularly directed to the use of alkali phenates as the oil soluble promoter to be used with the sodium hydroxide. Alkali phenates may be used as such or phenols may be employed. As caustic is also used in the process of this invention, the caustic will react with phenols to give "alkali phenates. It is particularly contemplated that the compounds widely known as petroleum Referring to .this table .it will be .noted that the first test runemployed 133% 'of-the amount of sodium hydroxide required to fully neutralize esters present in the oil. The first test was conductedemploying sodium hydroxide alone without the vuse of any ,oil-soluble promoter. It will be ,noted that even thoughaconsiderable excess of sodium hydroxide was employed, sulfur dioxide evolution was not completely eliminated. The actual reduction in sulfur dioxide evolution as compared to the distillation of a stock with no treatment was 63%. The deposit formed on heater tubes constituted about 0.60 gram of .a hard, brittle deposit which was exceedingly difficult to remove.

The. second test conducted asv shown in Table I employed. of the amount of sodium .hydroxide required to fully neutralize esters present in the Oil together with 2% .of the oil soluble promoter, crude sodium naphthenate. In

this case, the use of the crude sodium naphthenate together with considerablyless caustic was successful in materially reducing the sulfur dioxide evolution; the actual reduction being 85% as compared to the 63% reduction when no promoter was employed. However, it will be noted that the amount of deposit formed materlally increased constituting about .88 gram. From these two runs it is apparent that use of an oil soluble promoter with caustic is effective to reduce sulfur dioxide evolution, but does not reduce the amount of deposit formed. From these experiments, and others that will be cited,

it has been concluded that something less than 100% of the amount of caustic required to fully neutralize esters together with oil soluble promoters must be employed in order to materially reduce the amount of deposits formed during distillation.

This is borne out by the thirdexperiment indicated in the table, wherein only 95% of the amount of caustic was used which would theoretically fully neutralize the esters present. Crude sodium naphthenates in the amount of 2% were employed with this quantity of caustic, with the result that the deposit formed during distillation was materially reduced, about .24 gram of deposit forming. At the same time use of the smaller amount of caustic did not materially change the effectiveness with which sulfur dioxide evolution was eliminated, as an 86% reduction in sulfur dioxide evolution was attained.

One further point is to be made concerning the data indicated in Table I. In the case of the first two runs indicated utilizing 100% or greater of the theoretical amount of caustic required for full neutralization, not only was a deposit formed which was excessive in quantity, but this deposit was of a hard cement-like character which was exceedingly hard to remove from the heater tubes. However, in the case of the third experiment where less than the amount of caustic required for full neutralization was employed, not only was the amount of deposit materially cut down, but furthermore, the nature of this deposit was more favorable. The deposit formed in the third test was of a soft slimy character well adapted to ready removal from the heater tubes.

In order to more fully appreciate the advantages of this invention it is necessary to analyze more carefully the conditions which exist, and the effects which occur when employing different quantities of caustic and promoters. Consideration will first be given to the problem of sulfur dioxide evolution. Indicated in Table II below is the extent of S02 reduction which may be accomplished employing different quantities of sodium hydroxide.

TABLE II Distillation of Baltimore light catalytic naphtha (ester #33,6) showing treatment with caustic Referring to this table it will be noted that the catalytic naphtha treated had an ester number of 33.6. A petroleum oil having this ester number theoretically requires approximately pound of sodium hydroxide per barrel to attain complete neutralization of the esters. The first test which was conducted consisted of distilling the light catalytic naphtha without addition of any caustic or other basic material. It will be noted that about .46 gram of sulfur dioxide was evolved per liter of the oil distilled. These results were obtained by distillin the oil in glass to a still temperature of 340 F., the sulfur dioxide evolved dur ing distillation being collected in a sodium carbonate solution and titrated.

In the second test the stock was treated with /4 pound of sodium hydroxide per barrel. This amount of sodiumhydroxide represents approximately 50% of the quantity necessary for complete neutralization of the acid esters present. In this case about .41 gram of S02 were evolved indicating a reduction in sulfur dioxide evolution of about 12% In the third experiment which was conducted, /2 pound of sodium hydroxide per barrel of oil was employed during distillation.'- This amount of sodium hydroxide constitutes approximately the amount required to fully neutralize esters present. In this case the evolution of sulfur dioxide was further decreased somewhat, the actual percent reduction amounting to about 13%. It is significant, however, that even when employing a quantity of caustic sufficient to fully neutralize esters present, sulfur dioxide evolution was still comparatively great.

The fourth test conducted employed 1 pound of sodium hydroxide per barrel, which amount is approximately 150% times the amount required for full neutralization. In this case the sulfur dioxide evolution was reduced by 86%.

Considering the data presented in Table II, therefore, it is apparent-that elimination of sulfur dioxide evolution during distillation of a petroleum oil containing acid esters is relatively difficult when employing sodium hydroxide alone. In order to materially out down the sulfur dioxide evolution it is necessaryto employ a large excess of caustic. Considering the data of Table I, together with the data of Table II, it will be noted that use of oil soluble promoters together with the caustic materially cuts down the sulfur dioxide evolution. For example, comparing test 2 of Table I, with test 3 of Table II, in both of which tests approximately 100% of the theoretical amount of caustic was used which would be required for full neutralization, it will be noted that in the case where sodium naphthenate was employed, the reduction in sulfur dioxide evolution was as against a 13% reduction when no sodium naphthenate was employed. This data fully substantiates the conclusion that use of an oil soluble promoter with caustic during distillation materially contributes to the reduction of sulfur dioxide evolution. The tests show that when employing comparatively small amounts of an oil soluble promoter together with caustic, a reduction in sulfur dioxide evolution is possible materially less than that obtainable even when employing a great excess of sodium hydroxide alone.

In accordance withese principles, therefore, the present invention utilizes a combination of oil soluble promoter and sodium hydroxide which together are effective to substantially eliminate sulfur dioxide evolution during distillation.

This is furtherbrought out by Table III below in which sulfur dioxide evolution is recorded F7 when 'employing varying an loilhts bf caustic-and different types of oil soluble 'promoters. -'-In each case-by referring to T'able lI itwill be noted that use of a I small quantity or oil soluble: promoter i'with ai given amount of sodium hydroxide materially reduces the amount of sulfur dioxide evolved.

Distillation tests employingacid treated catalytic naphthw (ester -N0. 72)

N a'QH Added"to Stock lest Promoter Added, Volum' Per Cent I Per Cent LbsJBbl. oi Theoretical SOz Beduction Over Stock With N o Treatment .02% Petroleum Phenols. z J. '0'.;5%-'Sodium Naphthenate 0.25% Retroleum Phenols and 025% Heavy Crude Oil.

0% Sodium N aphthe'nelte;

Per" cent 9 Consideration will --nowbe given to the second problem encounteredin the distillation of oils formed as can -be achieved to permit less frequent fplant shutdowns -for cleaning of -disti1-1a- .1 -tion- "equipment. Data-"relatiye to ;-the extent of -,depbsit formation are given in Table IV.

:Heater fouling tests-acid treated-catalytic naphll tha ester numberZZ) "Heater NaOH Added A i v Quantity 5 --0il SolubleOrganic'lromoter of Number Theoretical Deposn Percent Gra ns 1 None -None... 0.2188 2 133 None. 035959 3 -l33 .02 Vol. Per'Cent- Petroleum 0.6768

Phenols. 4 133 2 Vol.- Per Cent Crude Na 0.8843

N eiphthenate. 133 0.08 bsL/Bbl. Tetra ink Am: 4281 inonium' Hydroxide. 1 -6 100 0.5 Vol. Per Cent Crude Na 6470 Naphtheriate. 7; "-95 2.0 'Vol-E- Per Cent-Crude Na .2368

Naphthenate.

Jout -.the addition "ofany c'austic-"or organicprotest number one, and yieldeda deposit of about .22 gram. Inrepeating this experiment employing'133% of the amount of caustic requiredto fully neutralize esters present in the naphtha, a greater deposit was obtained" amounting to about '.60 gram as indicated in experiment number-two. In the third and fourth experiments the same amount of excess causticw'as 'used- -but a small quantity of petroleum phenols'and crude sodium naphthenate respectively were'added'to the catalytic-naphthacontaining the caustic. In these experiments the amount of depositagain increased in-eachcase, amounting to about 0:68 and 0.88 gram respectively. Ina similar eX- periment in which the promoter used was tetra ethanol ammoniumhydroxide as shown: by run number-five, the amount ofdeposit was-somewhatless'amounting to about .43 gram. --Again, however, this amount of deposit is materially greater than' when the catalytic naphtha is distilled-Without theaddition of any acid ester neutralizingsubstances.

The-sixth experiment conducted employed only that amount of caustic required to completely neutralize the acid esters together with-0.05vo1- ume percentof crude sodium -naphthenate. In this expediment it-was found" that the-deposit formation was still extremely high. In the'last experiment= conducted less than the theoretical amount of caustic was used together with 2 'volume percent of crude sodium naphthenate. In this case the amount of Y deposit was materially reduced, yielding 0.24 gram. It will be noted that this amountoi deposit'compares favorably with the de'posit formed on distillation of the catalytic naphtha when no caustic or promoters are added.

The conclusion to be drawn from Table IV, therefore, is that the amount of deposit formation is excessive when caustic is employed amounting to or greater, of the amount required-tofully neutralize acid esters presentin the oil being distilled. However, when'less'than the theoretical amount of caustic requiredto fully 'neutralize the esters'is employedtogsther witha suitable oil soluble organic promoter, the amount of deposit is materially reduced, approaching the quantity of deposit formed when'no acid"'ester neutralizingsubstancesare 'employe Considering the second aspect of deposit formation during distillation, experiments are indicated in Table V relative to the nature of the deposit formed during distillation. In Table V, eight experiments are indicated with varying amounts of caustic andemploying different or-- ganic promoters.

TABLE V Heater fouling tests-acid treated catalytic naphtha (ester number 7.2)

Heater N aOH Added Foulas Free Caustic,

Oil Soluble Organic Promoter Number Theoretical Nature of Deposit Formed Per Cent 1 None None Bar 2 133 None 3 133 .02 Vol. Per Cent Petroleum Phenols 4 133 0.08 Lbs./Bbl. Tetra Ethanol Ammonium Hydroxide. 95 2 Vol. Per Cent Crude Na N aphtbenate. 95 2 Vol. Per Cent deashed Crude Na d, black, tightly adhering. Do.

Do. Hard, tightly adhering.

Semi-soft deposit, loose, some clean tube. Semi-soft deposit, Brownish deposit.

N aphthenate. 7 1 84 .25 Per Cent Petroleum Phenols N on-adhermg, dark deposit. 8 1 70 08 Lb./Bbl. Tetra Ethanol Ammonium Slight amount of flocculent precipitate.

Hydroxide.

1 Tests conducted in glass distillation equipment.

Referring to this table, it will be noted that in the case where no caustic is added to the catalytic naphtha being distilled, a hard, black, tightly adhering deposit is obtained. This deposit on analysis was found to contain chiefly coke, or carbonaceous material formed as a result of decomposition of organic materials during the heater fouling test. Similarly in the case of experiments 2, 3 and 4 where an excess of sodium hydroxide was used, the deposit formed was of a similar character being hard, black and tightly adhering. The character of this deposit was not changed by the addition of organic promoters as in experiments 3 and 4. On analysis this deposit appeared to be principally carbonaceous material formed from coking of organic materials but comprising a large portion of sodium sulfate. In the remaining experiments listed in Table V less than the'quantity of causic was employed which would be required to fully neutralize the acid esters present. In addition a small quantity of organic promoters were employed as indicated in the table. In each case where less than the theoretical amount of caustic was used, the deposit obtained was no longer hard and tightly adhering, but was at least partly soft and was of a nature that could be easily removed from the heater tube.

The conclusion to be drawn from the data of Table V therefore is that a hard tightly adhering undesirable formation appears Whenever a quantity of caustic is used exceeding that required for neutralization of acid esters present. Furthermore, an undesirable type of deposit is obtained when no caustic whatever is added to the oil being distilled. However, when less than the amount of caustic is employed which would fully neutralize acid esters present together with a small quantity of organic promoters, a deposit is obtained which is materially softer and may be more readily removed from heater tubes.

Summarizing briefly the results of the experiments indicated, the data of Tables II and III related to the problem of sulfur dioxide evolution during distillation from oil which has been together with an amount of caustic which may be less than that quantity required to fully neutralize acid esters present. The data presented in Table IV indicated that an excessive quantity of deposit is obtained whenever or more of the theoretical amount of caustic is used, while materially less deposit is obtained when a small percent of crude sodium naphthenate, or similar promoter is added to the oil being distilled. The data presented in Table V bore out the fact that a hard, dimcult to remove type of deposit is obtained whenever an excess amount of caustic is used, while a softer more easily removed deposit is obtained when less than the theoretical amount of caustic is employed.

Data of the nature indicated leads to an :indication of the mechanism involved in the distillation of acid treated petroleum oils. As regards sulfur dioxide evolution, it is apparent that when no substance is added which will react with the acid esters present. sulfur dioxide evolution will be great, and that the sulfur dioxide evolution may be decreased by utilizing caustic or other basic materials which will react with the esters or sulfur dioxide formed. Furthermore, it is significant that a comparatively small amount of an organic promoter will materially increase the eifectiveness with Which caustic decreases suliur dioxide evolution. As a result of employing ester neutralizing substances to cut down sulfur dioxide evolution, the amount of deposit formed is increased. Particularly significant is the fact that the quantity and nature of deposit is critically a function of the amount of caustic used. The probable mechanism of these effects may be indicated using as an example petroleum phenols. In distilling a petroleum oil containing acid esters in the presence of caustic and petroleum phenols, the caustic first reacts with the petroleum phenols to give sodium phenate. The sodium phenate then reacts with acid esters to form the sodium salt of the acid esters and petroleum phenols. The petroleum phenols then react with the caustic present to re-form sodium phenate. This sodium phenate ganic promoters such as tetra ethanol ammo- ..niumhyd-roxide, and the other promoters indicated. Ineach case the promoter reacts with the acid ester to form a salt of the ester plus a substance which will react with the caustic to form more promoter. It appears that this chain of reactions is successful in materially promoting the reaction of the caustic with the esters to suppress sulfur dioxide evolution.

Considering this mechanism as it affects deposit formation, it is apparent that the data presented that the presence of caustic alone, or the presence of an excess amount of caustic over that required to neutralize esters results in the formation of sodium sulfate and in the formation of a hard, tightly adhering deposit. Whenever an excess of caustic is present the presence of organic promoters can not prevent formation of this type of deposit since free caustic will still remain after the promotional reaction with the acid esters present. However, in the case where less than the theoretical amount of, caustic is employed, the promoters can successfully cause the caustic to be used in neutralizing the acid esters leaving no free caustic to form the troublesome deposits referred to.

'Theconclusion to be drawn from'these'considerations, therefore, is that in distilling an acid treated-oil itis necessary to utilize a substance which will reactwith the acid esters present to prevent evolution of sulfur dioxide. Caustic alone is not a desirable agent for this purpose since an excess amount of caustic is necessary and since a large quantity of hard deposit is formed which is difiicult to remove. Furthermore, use of organic promoters with an excess L amount of caustic, while effective in substantially eliminating sulfur dioxide evolution is not effective in eliminating the troublesome deposits formed. Consequently, in accordance with this invention an amount of caustic is used which does not exceed that required to fully neutralize acid esters together with a small amount of organic promoter.

As formerly indicated, a wide variety of organic promoters may be used. It has been found, however, that sodium naphthenates, alkali phenates and tetra-alkyl ammonium hydroxides are .particularly suitable for this purpose. Indicated below are examples of the eficacy of these agents in accordance with the process of this invention.

Emample I An acid treated catalytic naphtha was distilled in a laboratory type glass still and was treated in a laboratory type heater fouling test which closely simulated the operation of plant equipment under similar conditions. The catalytic naphtha was distilled in the presence of 95% of the amount of caustic required to fully neutralize acid-esters present, together with 2% of crude sodium naphthenates. The deposit formed in thistest amounted to 0.24 gram, and the reduction in evolution of sulfur dioxide amounted to 86% as compared to tests wherein untreated catalytic naphtha was distilled. It will be noted that the amount of deposit formed was materially less than the comparable figures formerly indicated, employing 100% or more of the amount of caustic-required to neutralize the es ganic promoters.

1'2 ters. Furthermore, the sulfur dioxide-evolution was substantially eliminated.

Example I] An acid treated light catalytic naphtha having an ester number of 53.8 was distilled in av laboratory type. glass distillation apparatus. The catalyticnaphtha was distilled in the presence of approximately vtwo-thirds of the amount of causticrequired to achieve full neutralization, to-

- gether with one part per five thousand parts of a a heart, cuter petroleum phenols. An reduction in sulfur dioxide evolution was obtained as compared to the distillation of this same stock without caustic or promoter and a slight amount of sediment was obtained which was of aaloose nature and did not adhere to the equipment.

Example III cent reduction of sulfur dioxide evolution was 100%, no sulfur. dioxide being evolved. The. deposit formed during distillation was of light color, iiocculent in nature and slight in amount.

1 Inaccordance withthepresent invention it is contemplatedlthat a preferred manner. of dis.- tilling petroleum oils whichlhavebeen acid treated and hence. haveacid. esters. present, is to employ less than 100% of the amount of caustic required to fully neutralize the acid esters together with a smaller quantity of tetra ethanol ammonium hydroxide, or an alkali phenate. The preferred type of alkali phenate whichmay be employed is soduim phenolate, although potassium phenates may also be used.

A preferred manner of conducting. the process of this invention is to utilize from to of the amount of caustic required'to fully neutralize esters present in the oil, and to add from 10% to 5% of the quantity of the particular 'organic. promoter which would alone be sufiicient to fully neutralize the esters. However, it is within the scope of this invention to use any, quantity of caustic less than that required to neutralize esters present plus a small amount of the or- For example, the benefits of this invention may be obtained by utilizing about 90 to 95% of the theoretical amount of caustic required to fully neutralize acid esters together with aboutZ to 5% of the theoretical amount of petroleum phenols. 'In accordance with the data presented in this specification it will be'noted that practice of the invention according'to the preferred procedure is best adapted to substantially eliminate sulfur dioxide evolution to minimize deposit 'formatiomand to resultin a soft, readily removable deposit.

What is claimed is: l V

1. In a process in which an acid treated mineral oil containing acid esters is distilled the improvement which comprises adding to the said oilduring distillation somewhat less than %"of the amount of alkali required to theoretically fully neutralize the said acid esters together with a small quantity of petroleum phenols.

2. The -improvement according to claim 1 wherein the alkali is caustic.

3. The improvement according to claim 1 wherein from 90% to 95% of the theoretical amount of alkali is added and from'2%to5'% of the theoretical amount of petroleum phenols REFERENCES CITED required to fully neutralize the said esters is The mnuwmg references are of record m the fhe improvement according to claim 1 me or this patent: wherein the said process i for distilling an acid 5 UNITED STATES PATENTS treated mineral oil containing acid esters com- Number Name Date prises distillation of a cracked naphtha. 2,393,531 Hart Jan. 22, 1946 5. A process for distilling a cracked naphtha 2,408,011 Walsh et a1 Sept. '24, 1946 in which 90 to 95% of the quantity of caustic is 2,455,679 Jones et al -L Dec. 7, 1948 added which would theoretically neutralize acid 10 esters present together with from 10% to 5% of the quantity of alkali phenates which would fully neutralize-the said acid esters.

MINOR C. K. JONES. EDWARD C. EULHARDIL 154 

1. IN A PROCESS IN WHICH AN ACID TREATED MINERAL OIL CONTAINING ACID ESTERS IS DISTILLED THE IMPROVEMENT WHICH COMPRISES ADDING TO THE SAID OIL DURING DISTILLATION SOMEWHAT LESS THAN 100% OF THE AMOUNT OF ALKALI REQUIRED TO THEORETICALLY FULLY NEUTRALIZE THE SAID ACID ESTERS TOGETHER WITH A SMALL QUANTITY OF PETROLEUM PHENOLS. 